If you are one of the lucky mathematicians (there are 509 of them) who has written a paper with Paul Erdös, then your Erdös number is 1. If you wrote a paper with a person whose Erdös number is 1, then your Erdös number will be 2. And so on.
My Erdös number is 2, because I wrote a paper (see here) with Professor Charles Chui whose Erdös number is 1, because Charles Chui wrote a paper with Paul Erdös (see here: On changes of signs in infinite series).
Erdös number of 2 is the largest it can be for anyone (from now on) since Paul Erdös is no longer alive. Sadly, he passed away in September 20, 1996. The Wikipedia page about him is here.
The Erdös Number Project studies research collaboration among mathematicians. To find out more about it and possibly discover your own Erdös Number, please go to here. Also, the social graph of Erdös is found here.
PS: For a while, I thought my Erdös number is 3 since I wrote several papers with Ömer Eğecioğlu who wrote papers with Charles Ryavec who wrote a paper with Paul Erdös (see here: A characterization of finitely monotonic additive functions). Thanks to Emilie Menard Barnard and Keith Avery for pointing out my paper with Professor Charles Chui of Texas A&M, who by the way was one of the nicest persons I have ever met in my life. He is now retired. Long live Charles. My best wishes. My best wishes to Emily and Keith too, of course.
A Bright Child knows the answers, is interested, attentive, has good ideas, works hard, answers the questions, performs in the top group, listens with ease, needs 6-8 repetitions for mastery, understands ideas, enjoys peers, grasps the meaning, completes assignments, is receptive, copies accurately, enjoys school, absorbs information, is a ‘technician’ of sorts, is a good memorizer, enjoys straight forward and sequential presentations, is alert and is pleased with his/her own learning.
A Gifted Child asks the questions, is highly curious, is mentally and physically involved, has wild and silly ideas, plays around yet tests well, discusses in detail and elaborates, is beyond the group, shows strong feelings and opinions, already knows, 1-2 repetitions for mastery, constructs abstractions, prefers adults, draws inferences, initiates projects, is intense, creates a new design, enjoys learning, manipulates information, inventor, good guesser, thrives on complexity, is keenly observant, and is highly critical.
Taleb asks: “You are rich, how come you are not smart?”
I ask: “You are poor, how come you are smart?”
Answer: I chose not to accumulate.
As the medical science and practice are advancing, transplanted organs work better in new bodies, making the need for organs more apparent; however, in economic terminology, supply is way behind the demand curve:
“Organ transplants are one of the extraordinary developments of modern science. They began in 1954 with a kidney transplant performed at Brigham & Women’s hospital in Boston. But the practice only took off in the 1970s with the development of immunosuppressive drugs that could prevent the rejection of transplanted organs. Since then, the number of kidney and other organ transplants has grown rapidly, but not nearly as rapidly as the growth in the number of people with defective organs who need transplants. The result has been longer and longer delays to receive organs.” 
So, where do we get new organs, if there are not sufficiently many people willing to let go? Perhaps, science can help us here: what about growing organs in the lab?
Of course, as usual, fiction (or rather, science-fiction) has already offered several other alternatives to producing organs in factories: for example, cloning people in order to harvest their organs later on. You can read several science-fiction stories and watch movies with this theme; here two recent ones: Never Let Me Go (2010) and Moon (2009).
This is fiction, of course.
The reality is however is on its way; two economists: “Mr. Becker is a Nobel Prize-winning professor of economics at the University of Chicago and a senior fellow at the Hoover Institution. Mr. Elias is an economics professor at the Universidad del CEMA in Argentina,” offer the following solution: You can sell your organs.
Well, we spoke about suply/demand curve above, so economists feel qualified to chip in. They give analyses and examples on how and why this might work.
Who is “you” above? You is the one that “needs” the money, obviously, poor people. And, who might possibly “buy”. Rich people, of course. Poor selling their kidneys to the rich would be morally acceptable to some, since we live in capitalism.
But what should the rich stop there? As, my friend Mark Gannon puts it “…because the next logical step for capitalism is for the poor basically to be kept around so their organs can be harvested for use by the rich. We all know only those who have money ought to be able to get organs for transplant!?”
Still, Mark’s scenario is probably more humane than the following: Sending mercenaries to harvest organs in other countries; armed with guns and scalpels. A new form colonialism, I suppose. Perhaps as the ships carried live bodies of Africans as slaves to Americas up to the 19th Century, our high-tech, refrigirated airplanes would be flying from all unfortunate places to the Elysium, filled with live organs.
It seems that while the West ascends to other solar systems or perhaps to other galaxies on the wings of science, they also have the capacity to descend into the moral oblivion even deeper.
 Cash for Kidneys: The Case for a Market for Organs. The Wall Street Journal, January 18, 2014.